Camshaft phasers are known for changing the phase relationship between a crankshaft and a camshaft in an internal combustion engine in order to achieve desired engine performance. U.S. Pat. No. 5,507,254 to Melchior, hereinafter referred to as Melchior, teaches a camshaft phaser comprising a rotor with an outward extending vane and a stator with an inward extending lobe such that the rotor is located within the stator and the vane and lobe together define and advance chamber and a retard chamber. Oil is selectively supplied to either the advance chamber or the retard chamber and vacated from the other of the advance chamber and retard chamber as directed by a phasing oil control valve in order to rotate the rotor within the stator and thereby change the phase relationship between the camshaft and the crankshaft. It is also known in the camshaft phaser art to provide the rotor with a plurality of vanes and to provide the stator with a plurality of lobes, thereby defining a plurality of alternating advance chambers and retard chambers. Melchior also teaches that the phasing oil control valve that may be rotated in order to supply and vacate oil from the advance chamber and the retard chamber. The phasing oil control valve is directly and mechanically rotated by an arm that is sensitive to engine speed such that the rotational position of the phasing oil control valve determines the rotational position of the rotor relative to the stator. The valve spool defines a first recess and a second recess separated by a rib such that one of the recesses acts to supply oil to the advance chamber when a retard in timing of the camshaft is desired while the other recess acts to supply oil to the retard chamber when an advance in the timing of the camshaft is desired. The recess that does not act to supply oil when a change in phase is desired does not act as a flow path. Rotating the phasing oil control valve directly and mechanically by an arm that is sensitive to engine speed may not be adequate for operation because modern internal combustion engines rely on many parameters, typically provided by various sensors which monitor various aspects of engine performance, processed by an electronic processor, for example an engine control module, to determine a desired camshaft phase. Consequently, it is desirable to rotationally position the phasing oil control valve taking into account any number of engine performance indicators.
What is needed is a camshaft phaser which minimizes or eliminates one or more of the shortcomings as set forth above.